Do you think the ECU is picking up false knock? Could be KC unrelated to what's occurring in the combustion chamber?
I suspect that the ECU is clinging onto its 87 octane roots as some conservative safety mechanism when it does this.
DRtuned specifies ONLY running 93 oct fuel. My experience tuning none Skyactive cars, when running lower octane, we run lower timing and compression. I have not compared OEM log to my tuned logs to see how much David increased timing and boost. My first conversation with David, he said they changed many things, including timing and boost.
It could be false knock from a crack in the road, the suspension or exhaust. Again, back on my Hemi V8 EFI tuning, we saw false knock from an aftermarket exhaust pipe touching the frame, something loose or the diff. I have a many hours chasing down and correcting false knock.
After I satisfied my tuner we had eliminated mechanical items causing false knock, he reduced the sensitivity of the knock sensors. As we went along and read spark plugs to the tunes he turned the knock sensor off.
As an aside, the Hemi knock sensors are tuned at the factory for a stock engine/exhaust. We change the engine displacement, cam, intake and throttle body. We ditched the factory exhaust for headers and larger diameter, high flow exhaust. These items changed the frequency of knock detection. In the end, we relied on reading the plugs, looking for knock. We couldn't hear knock over the exhaust noise. For these reasons, I have used a new spark plug, ran a WOT and stopped ASAP. Then replaced the plug so I could look at the plug under a magnified glass, looking for specs off the pistons from detonation or knock. Also we can see fueling and timing at higher load and RPM.
Even if my tuner doesn't use this information, it's a second look of what is going on in the combustion chamber. If I saw something, I would flag the tuner. So far he has been tuning on the conservative side. I like that in my DD. Racing, looking for max effort power, we tune to the aggressive side and use spark plug reading to confirm the electronics. Today, we use 8 ECT sensors monitoring the health of each cylinder. If one hole runs lean, high EGT, the software removes all the timing from the engine and alarms the driver.
Word of caution, tuners do not fix an engine his tune damaged. His reputation will suffer but that is the extent. I have personal experience with an expensive NEW race engine that last less than 10 minuets before it lost compression and started smoking. The engine ran very lean on E85 and melted several pistons. Needless to say I was unhappy.
Consider working with a tuner who has experience with DD 2.5l engines. Review the logs you send to the tuner, looking a KC, timing, boost, ect. Final check is reading a plug once or twice. The tuners is getting info after the combustion event and an average AF value. IF one injector is running lean, he most likely will not detect it.....as me how I KNOW. Our 2.5l plugs are easy to get to and it only takes 5 minuets to swap out.
